No CH, No HW, Pump is always on

KDJ

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Hi,

Our central heating and hot water have both failed today. However the pump is always on. Here's a description of the system:

Fully sealed with expansion tank.
Two zone valves
RF room thermostat with receiver next to hot water cylinder

Here's what I've tried:

Make sure there is no demand for CH or HW...pump is still running, all pipes are cold.
Switch off system at fuse, pump stops
Switch on system at fuse, pump starts even though there is still no demand for CH or HW.
Set programmer to request HW (but not CH), zone valve makes whirring noise (presumably motor), zone valve clicks (presumably microswitches). Check boiler - neon indicator says there is no demand.
Set programmer to request CH (but not HW), both zone valves make whirring noise, both zone valves click. Wait for RF room 'stat to request heat, green LED illuminates on receiver. Check boiler - neon indicator says there is no demand.
Repeat steps above with programmer set to request both CH and HW. Same result.

It also sounds as if there is no water being pushed around the radiators.

I've tried wiggling the levers on both of the zone valves and that does nothing either.

Any ideas please? Thanks.
 
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KDJ

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no water in pipes?
blockage?

The exapansion cylinder pressure needle is at 1.5 bar. I've tried the bleed valve on two radiators and water seeped out. Is this sufficient evidence that there's water in the system? I'm not sure how to check for a blockage though.

Even if there is a blockage should I still expect the boiler to indicate that heat is required?
 

DP

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System description would suggest you do not have a boiler. That could be the reason why you have no hot water or heating
 
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It's possible there may be a frost stat wired into the system, if so it would override the other controls, the pump should/would therefore be running, but the boiler should also ignite. Assuming you've checked the pilot light [if any] is lit and the boiler stat is not in off position, there may be a reset button
 
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Sorry forgot to mention, check the gauge to ensure pressure in system is adequate, if not there's probably a filling loop local to boiler.
 

KDJ

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DP said:
System description would suggest you do not have a boiler. That could be the reason why you have no hot water or heating

Yep - the exterior oil-fired boiler is still there!

jimhet said:
It's possible there may be a frost stat...Assuming you've checked the pilot light [if any] is lit and the boiler stat is not in off position, there may be a reset button

I'm sure there is no frost 'stat but thanks for this tip. There is no pilot light (see previous comment - it's an oil-fired boiler in an exterior wall-mounted cabinet). I'll have a look for a reset button. Do you think the neon indicator shows "boiler WANTS TO make heat [i.e. has demand]" or "boiler IS making heat [i.e. burning oil]"?

jimhet said:
check the gauge to ensure pressure in system is adequate

The pressure shown on the expansion cylinder in the airing cupboard is 1.5 bar. There is no pressure indicator on the boiler. A bleed key on one random radiator suggests there is water in the system.

Thanks for all of the advice so far. One specific question: the zone valves are Honeywell with 5 wires. Yellow/Green is obviously earth. Are there any standard colours for the remaining wires? Presumably two of them are live/neutral to power the motor and two of them are the contacts of a normally-open micro-switch?
 
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I'm sure there is no frost 'stat but thanks for this tip. There is no pilot light (see previous comment - it's an oil-fired boiler in an exterior wall-mounted cabinet). I'll have a look for a reset button. Do you think the neon indicator shows "boiler WANTS TO make heat [i.e. has demand]" or "boiler IS making heat [i.e. burning oil]"?

It would be very remiss of any boiler manufacturer or installer to have an EXTERNAL boiler without a frost stat to protect against freezing.

Its not at all clear to me why you are staying indoors without looking at your boiler!

The first thing I would do if I was called is to check at the boiler to see if these is a call for heat. That originates from the orange wire on the motor valve.

If no call for heat when the controls are correctly set then I would work BACKWARDS from the boiler to see where it fails.

Tony
 
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have you got oil?
what oil boiler/burner ?
does it have an overheatstat?
has the burner locked out?
more questions later.
 

KDJ

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Agile said:
...EXTERNAL boiler without a frost stat...staying indoors without looking at your boiler...check at the boiler to see if these is a call for heat. That originates from the orange wire on the motor valve...If no call for heat when the controls are correctly set then I would work BACKWARDS from the boiler to see where it fails.

Thanks Tony this is very helpful. I have been outside because the neon indicator I've described is inside the external cabinet co-located with the boiler.

I've spent an hour delving through instructions left by the previous occupants but with no success so I'll look for a name plate and serial/model number to see if I can find some instructions on the Internet.

numpty1 said:
have you got oil? what oil boiler/burner? does it have an overheatstat? has the burner locked out?

There is definitely oil in the tank and oil in the Tiger loop (?) I'm still trying to identify the boiler; it's build style suggests it's not a recent model. The switch marked "Reset" had no effect. To answer the overheat 'stat question I need to find more information about the model.

Thanks again for all of the advice so far...it's much appreciated.
 
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sounds that micro switch is sticking, swap both 2 port valves , i am no sparky but have had this problem on a few occasions , changed the valves and it cured the problem, worked for me.
 

KDJ

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Thanks for all of the advice. The problem is now fixed. There were two issues. First the boiler was in lockout. It took me far too long to find the reset mechanism. Once the boiler was reset then the pump no longer came on "by itself" when there was no demand. From this I've learned that the boiler must have some independent control of the pump (presumably a frost 'stat). Second is that the RF room 'stat seems badly located. At random times the RF receiver would receive an "OFF" command even though the RF transmitter displays that the room is not yet up to temperature. A combination of new batteries and a better location for the transmitter has fixed this problem.
 

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